1. Field of the Invention
This invention relates to a linear type vibration motor in which travelling vibration wave is generated on vibratory members to frictionally drive a moving member, and in particular to the structure of the vibratory members thereof.
2. Related Background Art
The direction of the normal in the present invention will be defined here on the basis of FIG. 6 of the accompanying drawings. In FIG. 6, reference numeral 2 designates a vibratory member on which a travelling vibration wave is generated, reference numeral 3 denotes a moving member frictionally driven by the travelling vibration wave, letter U designates a direction in which the travelling vibration wave travels, and letter N denotes a direction in which the moving member 3 is moved. Reference numeral 10 designates the vibration plane of the travelling vibration wave generated on the vibratory member 2, and arrow 20, perpendicular to plane 10 and pointing to the moving member 3 from the vibratory member 2, is defined as the direction normal to the vibration plane 10.
In recent years, numerous vibration wave motors have been proposed in which a frequency voltage is applied to an electrostrictive element to thereby generate a travelling vibration wave on a vibratory member and drive a moving member which is in frictional contact with the vibratory member. However, such vibration wave motors have suffered from a drawback in that the vibratory member is single and the drive force is small. A vibration wave motor in which a plurality of vibratory members, for example, two vibratory members, are provided to overcome such a disadvantage is disclosed, for example, in U.S. Pat. No. 4,562,374. However, the linear type vibration wave motor disclosed in this patent is of the type in which two vibratory members for transmitting a drive force to impart a strong drive force to a moving member sandwich the moving member therebetween. In the vibration wave motor of such construction, there has been a drawback in that the advantage which should originally be a feature of a thin and compact vibration wave motor is reduced. Also, in the case of such a linear type motor, in which the moving member is sandwiched, the moving member is restricted to a planar shape. Other conveyed objects cannot be placed on the moving member, because they were placed on the moving member, the conveyed object would be damaged.